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Abstract:

There is a problem that if a transmitter apparatus having an adaptive
modulation function is to be configured to divide data for transmission,
the structure of the transmitter apparatus will be complicated and the
cost thereof will be raised. In order to solve this problem, a
transmitter apparatus comprises: a dividing means for dividing input data
into a plurality of pieces of data; a plurality of transmitting means for
transmitting the pieces of data as divided to respective transmission
paths; and a modulation scheme deciding means for deciding, from among
modulation schemes associated with the conditions of the transmission
paths, a modulation scheme, which is to be used by the transmission
means, such that the difference in transmission speed between the pieces
of data transmitted by the plurality of transmitting means is within a
predetermined range.

Claims:

1.-10. (canceled)

11. A transmitter apparatus, comprising: a dividing unit for dividing
input data into a plurality of pieces of data; a plurality of
transmitting unit for transmitting the pieces of data as divided to
respective transmission paths; and a modulation scheme deciding unit for
deciding, from among modulation schemes associated with the conditions of
the transmission paths, a modulation scheme, that is to be used by the
transmission unit, such that a difference in transmission speeds between
the pieces of data transmitted by the plurality of transmitting unit is
within a predetermined range.

12. The transmitter apparatus of claim 11, wherein the modulation scheme
deciding unit decides the predetermined range on the basis of a range of
the transmission speed where a receiver apparatus for receiving the
pieces of data as transmitted is capable of receiving the pieces of data.

13. The transmitter apparatus of claim 11, wherein the modulation scheme
deciding unit decides the modulation scheme that is to be used by the
transmission unit such that the transmission speeds between the pieces of
data as divided transmitted by the plurality of transmitting unit accord
with each other.

14. The transmitter apparatus of claim 11, further comprising: a
determining unit for instructing the dividing unit to stop dividing the
data on the basis of failure information generated by the transmitter
apparatus or failure information generated by a transmitter apparatus
that is opposed to the transmitter apparatus.

15. The transmitter apparatus of claim 11, further comprising: a
plurality of receiving unit for receiving the plurality of pieces of data
that are divided and transmitted; and an integrating unit for integrating
and outputting the plurality of pieces of data.

16. A transmission system, wherein the transmitter apparatus of claim 15
is arranged so that the pieces of data as divided that are transmitted
from the transmitting unit of the transmitter apparatus are received by
the receiving unit of the different transmitter apparatus.

17. A transmission method, comprising the steps of: dividing input data
into a plurality of pieces of data; transmitting the pieces of data as
divided to respective transmission paths; and deciding, from among
modulation schemes associated with the conditions of the transmission
paths, a modulation scheme of the data, such that the difference in
transmission speeds between the pieces of data that is transmitted is
within a predetermined range.

18. The transmission method of claim 17, wherein the predetermined range
is decided on the basis of a range of the transmission speeds where the
pieces of data that are transmitted can be received.

19. The transmission method of claim 17, wherein the modulation scheme is
decided so that the transmission speeds of the pieces of divided data
accord with each other.

20. The transmission method of claim 17, further comprising instructing
to stop dividing the data on the basis of failure information.

21. A transmitter apparatus, comprising: a dividing means for dividing
input data into a plurality of pieces of data; a plurality of
transmitting means for transmitting the pieces of data as divided to
respective transmission paths; and a modulation scheme deciding means for
deciding, from among modulation schemes associated with the conditions of
the transmission paths, a modulation scheme, that is to be used by the
transmission means, such that a difference in transmission speeds between
the pieces of data transmitted by the plurality of transmitting means is
within a predetermined range.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a transmitter apparatus and a
transmission method which divide and transmits data, in particular a
transmitter apparatus, a transmission method and a transmission system
including an adaptive modulation function.

BACKGROUND ART

[0002] A technology is known, in which data is transmitted in parallel by
a plurality of transmitter apparatuses to enlarge a transmission capacity
of a transmission section. For example, a technology exists, in which
when data having a frame configuration, like a LAN (Local Area Network),
data is divided for each frame and transmitted in parallel by the
plurality of transmitter apparatuses. Patent document 1 and Patent
document 2 disclose the technology that data is divided and transmitted.

[0003] Patent document 1 discloses a configuration of a communication
device which forms a plurality of logical links with an opposite
communication device, and divides and transmits transmission data. The
communication device described in Patent document 1 synthesizes the
received data in order of a transmission number to restore the divided
data into the original data.

[0004] Patent document 2 describes a configuration of an edge device which
generates divided frames by dividing a MAC frame, a length of which is
longer than a predetermined length, which flows in the broad area
Ethernet network ("Ethernet" is registered trademark). When transferring
the divided frames from the network to the outside, the edge device
described in Patent document 2 combines the divided frames.

[0005] The communication device described in Patent documents 1 and 2
divides the transmission data and transmits them in parallel to enlarge
the transmission capacity.

[0006] As a method of optimizing the transmission capacity depending on a
condition of a transmission path, Patent document 3 describes an adaptive
modulation function. A transmitter apparatus with the adaptive modulation
device decides a modulation scheme on the basis of the condition of the
transmission path so that a transmission error is lower than an allowable
amount.

[0010] In the transmitter apparatus with the adaptive modulation function
described in Patent document 3, when the transmission data is divided and
the pieces of data are transmitted by the plurality of the transmitter
apparatuses, each transmitter apparatus which transmits the divided data
may choose a different modulation scheme. In general, data is transmitted
at different transmission speeds for different modulation schemes. Thus,
if the divided data is transmitted with the different modulation scheme,
the transmitter apparatus on the reception side may receive the data for
each piece of the divided data at a different speed.

[0011] Therefore, when the transmitter apparatus with the adaptive
modulation function divides the data and transmits them in parallel, the
transmitter apparatus on the reception side requires memory with a large
capacity for storing the pieces of data while the original data before
the division is restored from the received pieces of data. As a result,
when the divided data are transmitted using the transmitter apparatus
with the adaptive modulation function, a memory with large capacity
should be installed so that the configuration of the transmitter is
complicated and becomes costly.

[0012] Patent documents 1 to 3 do not disclose any means for solving the
problem which arises when the transmitter apparatus with the adaptive
modulation function divides data and transmits them.

[0013] An object of the present invention is to provide the means for
solving the problem described above.

Solution to Problem

[0014] The transmitter apparatus of the invention includes a dividing
means for dividing input data into a plurality of pieces of data, a
plurality of transmitting means for transmitting the pieces of data as
divided to respective transmission paths, and a modulation scheme
deciding means for deciding, from among modulation schemes associated
with the conditions of the transmission paths, a modulation scheme, that
is to be used by the transmission means, such that a difference in
transmission speeds between the pieces of data transmitted by the
plurality of transmitting means is within a predetermined range.

[0015] The transmission method of the invention includes dividing input
data into a plurality of pieces of data, transmitting the pieces of data
as divided to respective transmission paths, and deciding, from among
modulation schemes associated with the conditions of the transmission
paths, a modulation scheme of the data, such that a difference in
transmission speeds between the pieces of data that is transmitted is
within a predetermined range.

Advantageous Effects of Invention

[0016] The present invention includes the effect that when the transmitter
apparatus with the adaptive modulation function divides data and
transmits them, the transmitter apparatus does not get complicated and
price increase thereof is suppressed.

BRIEF EXPLANATION OF DRAWINGS

[0017] FIG. 1 is a diagram illustrating a configuration of a wireless
transmission system of a first exemplary embodiment.

[0018]FIG. 2 is a diagram illustrating division and integration of a MAC
frame in the first exemplary embodiment.

[0019] FIG. 3 is a diagram illustrating a processing procedure of the MAC
frame which is performed when one of data outputted by a frame dividing
unit is invalid data.

[0020]FIG. 4 is a diagram illustrating a configuration of a frame
integrating unit.

[0022]FIG. 6 is a diagram illustrating a wireless transmission system of
a second exemplary embodiment.

[0023]FIG. 7 is a diagram illustrating a configuration of a transmitter
apparatus of a third exemplary embodiment.

DESCRIPTION OF EMBODIMENTS

[0024] First Exemplary Embodiment

[0025] It is required that data is modulated using a modulation scheme in
which modulation level is large as much as possible, in order to enlarge
a transmission capacity of a wireless transmission system. However, as
the modulation level of the modulation scheme becomes large, resistance
of a wireless signal to variation of a transmission condition of a
wireless transmission path is generally reduced. On the other hand, if
the modulation level decreases, resistance of a wireless signal to
variation of a transmission condition increases though a transmission
capacity is reduced.

[0026] A wireless transmission system with an adaptive modulation function
optionally chooses a more suitable modulation scheme depending on a
transmission path condition to reduce a transmission error and enlarge a
transmission capacity. A procedure of the transmission system with the
adaptive modulation function is well-known. Detailed descriptions on the
adaptive modulation function are omitted.

[0027] FIG. 1 is a diagram illustrating a configuration of a wireless
transmission system of a first exemplary embodiment.

[0028] A configuration of a radio transmitter apparatus 10 is described
with reference to FIG. 1. In FIG. 1, a configuration and a function of a
radio transmitter apparatus 30 is the same as that of the radio
transmitter apparatus 10. Descriptions on the configuration and the
function of the radio transmitter apparatus 30 are omitted. A
configuration of a radio transmitting/receiving unit 19 of the radio
transmitter apparatus 10 is the same as that of a radio
transmitting/receiving unit 15. Detailed descriptions on the radio
transmitter apparatus 30 and the radio transmitting/receiving unit 19
are, therefore, omitted. In FIG. 1, each part of the radio
transmitting/receiving unit 19 corresponding to each part of the radio
transmitting/receiving unit 15 is given a reference numeral of the radio
transmitting/receiving unit 15 to which "A" is further added.

[0029] The radio transmitter apparatus 10 is opposed to the radio
transmitter apparatus 30, and the apparatuses transmit a MAC frame to
each other. The radio transmitter apparatus 10 divides an external LAN
signal 100 inputted from a user network 40, and transmits them to the
radio transmitter apparatus 30 as a radio signal. The radio transmitter
apparatus 30 restores data from the radio signal received from the radio
transmitter apparatus 10, and outputs it to a user network 50 as an
external output LAN signal 501.

[0030] On the contrary, the radio transmitter apparatus 30 divides an
external LAN signal 502 inputted from a user network 50, and transmits
them to the radio transmitter apparatus 10 as a radio signal. The radio
transmitter apparatus 10 restores data from the radio signal received
from the radio transmitter apparatus 30, and outputs it to a user network
40 as an external output LAN signal 231.

[0032] Relation of connection between parts of the radio transmitter
apparatus is mainly described below. Details of operations are explained
in a section "explanation on operations of the exemplary embodiment".

[0033] The frame dividing unit 11 receives the external input LAN signal
100 from the user network 40 and a division control signal 141 from the
transmission determining unit 14. The external input LAN signal 141 is a
MAC frame which is transmitted to the user network 50. The frame dividing
unit 11 divides the MAC frame of the external LAN signal 100 into two
parts, and outputs them to the generating unit 12 and the generating unit
13 as a divided LAN signal 111 and a divided LAN signal 112,
respectively.

[0034] The generating unit 12 receives the divided LAN signal 111 inputted
from the frame dividing unit 11 and a multiple alarm signal 142 inputted
from the transmission determining unit 14. The generating unit 12
multiplexes the divided LAN signal 111 and the multiple alarm signal 142
and outputs it to a radio transmitting unit 16 in the radio
transmitting/receiving unit 15 as a transmission signal 121.

[0035] The generating unit 13 receives the divided LAN signal 112 inputted
from the frame dividing unit 11 and a multiple alarm signal 143 inputted
from the transmission determining unit 14. The generating unit 13
multiplexes the divided LAN signal 112 and the multiple alarm signal 143
and outputs it to a radio transmitting unit 16A in the radio
transmitting/receiving unit 19 as a transmission signal 131.

[0036] The radio transmitting/receiving units 15 and 19 are described
below.

[0037] The radio transmitting/receiving unit 15 includes the radio
transmitting unit 16, a radio receiving unit 17, and an adaptive
modulation deciding unit 18. The radio transmitting/receiving unit 19
also includes the radio transmitting unit 16A, a radio receiving unit
17A, and an adaptive modulation deciding unit 18A. A configuration and
operations of the radio transmitting/receiving unit 19 are the same as
those of the radio transmitting/receiving unit 15. An explanation on each
part of the radio transmitting/receiving unit 19 is therefore omitted.

[0038] The radio transmitting unit 16 receives the transmission signal 121
from the generating unit 12. The radio transmitting unit 16 modulates the
transmission signal 121 on the basis of the modulation scheme designated
by a modulation control signal 181, and generates a radio signal 161. The
radio signal 161 is transmitted from an antenna 10A to an opposite
antenna 30A connected with the radio transmitter apparatus 30 as a radio
signal.

[0039] An antenna 10B connected with the radio receiving unit 17 receives
a radio signal 301 which is generated by the radio transmitter apparatus
30 and is transmitted by an antenna 30B via the antenna 10B. The radio
receiving unit 17 demodulates the inputted radio signal 301 and generates
a reception signal 172, and outputs the reception signal 172 to the
analyzing unit 20. The radio receiving unit 17 outputs a radio alarm
signal 171 to the transmission determining unit 14 and to the reception
determining unit 22. The radio alarm signal 171 includes a reception
power reduction alarm indicating that reception power of the radio
receiving unit 17 is reduced. The radio receiving unit 17 further outputs
a reception power monitoring signal 173 to the adaptive modulation
deciding unit 18.

[0040] The adaptive modulation deciding unit 18 recognizes radio reception
power of a signal received from the radio transmitter apparatus 30 which
is radio-opposed, from the reception power monitoring signal 173. The
adaptive modulation deciding unit 18 chooses a modulation scheme on the
basis of the magnitude relationship between the radio reception power and
a predetermined threshold value. The adaptive modulation deciding unit 18
outputs the chosen modulation scheme to the radio transmitting unit 16 as
the modulation control signal 181.

[0041] The adaptive modulation deciding unit 18 transmits and receives
information on the modulation scheme to and from the adaptive modulation
deciding unit 18A of the radio transmitting/receiving unit 19 using a
modulation scheme synchronization signal 182. As a result, the adaptive
modulation deciding unit 18 and the adaptive modulation deciding unit 18A
can recognize both of the modulation schemes which are chosen based on
the transmission signal 121 and the transmission signal 131.

[0042] The radio transmitting unit 16A of the radio transmitting/receiving
unit 19, the internal configuration of which is the same as that of the
radio transmitting/receiving unit 15 performs an operation which is the
same as that of the radio transmitting unit 16. That is, the radio
transmitting unit 16A modulates and frequency converts the transmission
signal 131 inputted from the generating unit 13, and generates a radio
signal 191. The radio transmitting unit 16A outputs the radio signal 191
to an antenna 10C.

[0043] The transmission determining unit 14 receives the radio alarm
signal 171, a radio alarm signal 192, a reception alarm signal 202, and a
reception alarm signal 212. The transmission determining unit 14 performs
a predetermined determining procedure based on conditions of the alarm
signals. The determining procedure is described in the section
"explanation on operations of the exemplary embodiment". The transmission
determining unit 14 outputs the determination result to the frame
dividing unit 11 as the division control signal 141. The transmission
determining unit 14 outputs the determination result to the generating
unit 12 and 13 as the multiple alarm signal 142 and a multiple alarm
signal 143.

[0044] The radio receiving unit 17 receives the radio signal 301 which is
received from the radio transmitter apparatus 30 which is the
radio-opposed station through the antennas 30B and 10B. The radio
receiving unit 17 frequency-converts and demodulates the received radio
signal 301. The radio receiving unit 17 outputs the demodulated signal to
the analyzing unit 20 as the reception signal 172. The radio receiving
unit 17 outputs the reception power reduction alarm indicating that
reception power from the radio transmitter apparatus 30 is reduced, to
the transmission determining unit 14 and the reception determining unit
22 as the radio alarm signal 171.

[0045] The radio transmitting unit 17A of the radio transmitting/receiving
unit 19, the internal configuration of which is the same as that of the
radio transmitting/receiving unit 15 performs an operation which is the
same as that of the radio transmitting unit 17. That is, the radio
transmitting unit 17A outputs a reception signal 193 to the analyzing
unit 21 and outputs the radio alarm signal 192 to the transmission
determining unit 14 and the reception determining unit 22.

[0046] The analyzing unit 20 receives the reception signal 172 and an
integration control signal 221. The analyzing unit 20 processes the
reception signal 172 based on the integration control signal 221, and
outputs the process result to the frame integrating unit 23 as an
integration LAN signal 201. The analyzing unit 20 outputs an alarm which
is detected from the radio alarm signal 171 to the transmission
determining unit 14 and the reception determining unit 22 as the
reception alarm signal 202.

[0047] The operation of the analyzing unit 21 is the same as that of the
analyzing unit 20 except that an inputted signal is the reception signal
193 which is outputted from the radio transmitting/receiving unit 19. The
analyzing unit 21 receives the reception signal 193 which is outputted
from the radio transmitting/receiving unit 19 and an integration control
signal 222 which is outputted from the reception determining unit 22. The
analyzing unit 21 performs predetermined processing on the reception
signal 193 based on the integration control signal 222 and outputs the
process result to the frame integrating unit 23 as the integration LAN
signal 211. The analyzing unit 21 outputs the reception alarm signal 212
informing of an alarm detected from the reception signal 193 to the
transmission determining unit 14 and the reception determining unit 22.

[0049] The reception determining unit 22 receives the radio alarm signal
171 outputted by the radio receiving unit 17 and radio alarm signal 192
outputted by the radio transmitting/receiving unit 19. The reception
determining unit 22 performs the following determination based on the
signals and outputs the determination result to the analyzing units 20
and 21 as the integration control signals 221 and 222, respectively.

[Explanation on Operations of the Exemplary Embodiment]

[0050] Operations of radio transmission system of the first exemplary
embodiment are described in detail with reference to FIG. 1 to FIG. 5.

[0051] The frame dividing unit 11 of the radio transmitter apparatus 10 of
FIG. 1 receives the external input LAN signal 100 from the user network
40 and the division control signal 141 from the transmission determining
unit 14.

[0052] The frame dividing unit 11 divides the MAC frame of the external
LAN signal 100 into two parts on the basis of the division control signal
141. The frame dividing unit 11 outputs one of the external LAN signals
100 divided into two parts to the radio transmitting/receiving unit 15
through the generating unit 12. The frame dividing unit 11 outputs the
other of the external LAN signals 100 divided into two parts to the radio
transmitting unit 19 through the generating unit 13.

[0053] When a division scheme in a time of division of the MAC frame
before transmission corresponds to that in a time of integration of the
MAC frames after reception, the MAC frame may be divided based on an
arbitrary procedure. For example, the MAC frame may be divided for each
even byte or for each odd byte in the frame. The MAC frame may be divided
into upper level bits and lower level bits for each one byte (eight bits)
of data which composes the MAC frame.

[0054]FIG. 2 is a diagram illustrating division and integration of the
MAC frame in the first exemplary embodiment. FIG. 2 illustrates, as an
example, a form of the MAC frame which is taken when the MAC frame which
is data with a unit of one byte (eight bits) (hereinafter referred to as
"BYTE data") is transmitted by dividing into upper level bits and lower
level bits.

[0055] S1 to S3 in FIG. 2 shows procedures of dividing the MAC frame into
two parts, upper level bits and lower level bits for one byte of data
which composes the MAC frame.

[0056] The upper level bits are the fifth bit to the eighth bit of data
which is formed by dividing the external LAN signal 100 in a unit of
byte, i.e. data indicated in 1-1, 2-1, 3-1, 4-1 . . . in FIG. 2. The
lower bits are the first bit to the fourth bit of data which is formed by
dividing the external LAN signal 100 in a unit of byte, i.e. data
indicated in 1-2, 2-2, 3-2, 4-2 . . . in FIG. 2. The frame dividing unit
11 divides the external LAN signal 100 (S1) into the divided LAN signal
111 (S2) which is composed of data of the upper level bits and the
divided LAN signal 112 (S3).

[0057] If the division control signal 141 instructs the frame dividing
unit 11 to stop dividing, the frame dividing unit 11 stops dividing the
MAC frame. When stop of dividing the MAC frame is instructed, the frame
dividing unit 11 transmits invalid data in an instructed direction of the
radio transmitting/receiving unit 15 or the radio transmitting/receiving
unit 19. The frame dividing unit 11 transmits the MAC frame without
division in the direction to which the invalid data is not transmitted.

[0058] Contents of the invalid data may be ones which can be recognized,
at the time of reception, that the data is not a divided MAC frame. If
all of the data are "0" or "1", and all of the data which is read out at
the time of reception are "0" or "1", the data may be decided as the
invalid data on the reception side. If the invalid data includes a
specific pattern, the data including the specific pattern may be decided
as the invalid data on the reception side when the specific pattern is
detected on the reception side.

[0059] FIG. 3 illustrates a procedure of the MAC frame which is performed
when one of the data which is outputted by the frame dividing unit 11 is
the invalid data.

[0060] S11 to S13 of FIG. 3 illustrates the MAC frames under a situation
that the divided data is not transmitted on the system where the lower
level bits are transmitted in FIG. 2, and the invalid data is transmitted
in place of the divided data thereon. The frame dividing unit 11
alternately outputs data of the upper level bits and data of lower level
bits in the external LAN signal 100 (S1) as the divided LAN signal 111
(S2). The frame dividing unit 11 outputs the invalid data as the divided
LAN signal 112 (S3).

[0061] Operations of the generating units 12 and 13 are described. The
generating units 12 and 13 in FIG. 1 only differ in an output
destination, i.e. the radio transmitting/receiving unit 15 or the radio
transmitting/receiving unit 19 from each other. A configuration and
operations of the generating unit 12 is the same as those of the
generating unit 13. The generating unit 12 is, therefore, described and
the generating unit 13 is not described.

[0062] The generating unit 12 multiplexes the divided LAN signal 111
received from the frame dividing unit 11 and the multiple alarm signal
142 received from the transmission determining unit 14. The generating
unit 12 inserts a synchronization pattern and an error detection code
into the multiplexed signal at constant intervals. The generating unit 12
outputs the transmission signal 121 generated in this way, to the radio
transmitting/receiving unit 15. The synchronization pattern and the error
detection code inserted into the transmission signal 121 at constant
intervals are detected by the radio-opposed station 30 and used for
estimation of transmission quality.

[0063] The generating unit 12 and the generating unit 13 work by the same
clock in the same apparatus. Therefore, the timing when the generating
unit 12 inserts the synchronization pattern and the error detection code
into the divided LAN signal 111 corresponds to the timing when the
generating unit 13 inserts the synchronization pattern and the error
detection code into the divided LAN signal 112.

[0064] The radio transmitting unit 16 receives the transmission signal 121
outputted by the generating unit 12. The radio transmitting unit 16
frequency-converts and modulates the transmission signal 121. The radio
transmitting unit 16 modulates the transmission signal 121 based on the
modulation scheme designated by the modulation control signal 181. The
radio transmitting unit 16 transmits the transmission signal 121 which is
frequency-converted and modulated to the antenna 30A of the radio
transmitter apparatus 30 opposed thereto as the radio signal 161 through
the antenna 10A.

[0065] The radio transmitting unit 16A performs the same operation as that
of the radio transmitting unit 16. The radio transmitting unit 16A
modulates and frequency-converts the transmission signal 131. The radio
transmitting unit 16A modulates the transmission signal 131 on the basis
of the modulation scheme designated by the modulation control signal
181A. The radio transmitting unit 16A transmits the transmission signal,
which is frequency-converted and modulated, to an antenna 30C of the
radio transmitter apparatus 30 through the antenna 10C as the radio
signal 161.

[0066] The adaptive modulation determining unit 18 transmits and receives
information on the modulation scheme to and from the adaptive modulation
determining unit 18A of the radio transmitter apparatus 19 using the
modulation scheme synchronization signal 182. The adaptive modulation
determining units 18 and 18A choose the modulation scheme in accordance
with a predetermined procedure so that transmission speeds on the
transmission signals 121 and 131 accords with each other. As a result,
the data transmitted by the radio transmitter apparatus 15 and the radio
transmitter apparatus 19 are received by the radio transmitter apparatus
opposed thereto, at the same speed.

[0067] The adaptive modulation determining units 18 and 18A can recognize
both the modulation scheme designated by the modulation control signal
181 and the modulation scheme designated by the modulation control signal
181A by the modulation scheme synchronization signal 182. Therefore, if
the modulation scheme, in which the transmission speed is the lowest, of
the modulation scheme recognized by the adaptive modulation determining
units 18 and 18A in common is chosen, the adaptive modulation determining
units 18 and 18A can choose the same modulation scheme.

[0068] The radio receiving unit 17 receives the radio signal 301 from the
radio transmitter apparatus 30 which is the radio-opposed station through
the antenna 30B and 10B. The radio receiving unit 17 frequency-converts
and demodulates the radio signal 301 and outputs it to the analyzing unit
20 as the reception signal 172.

[0069] The radio receiving unit 17 transmits information on a reception
alarm, which occurs due to a failure in the radio transmitter apparatus
15 and/or change of a transmission condition of a transmission path, to
the transmission determining unit 14 and the reception determining unit
22 as the reception alarm signal 171. The information on a reception
alarm includes, for example, an alarm indicating that the reception power
falls below a predetermined value. However, contents of the reception
alarm may be an alarm related to the condition of the transmission path,
the reception signal, or reception procedures, and are not limited to the
above example.

[0070] In the radio transmitting/receiving unit 19 the configuration of
which is the same as the configuration of the radio
transmitting/receiving unit 15, the radio receiving unit 17A
frequency-converts and demodulates the radio signal 302 and outputs the
reception signal 193 to the analyzing unit 21. The radio receiving unit
17A outputs the radio alarm signal 192 detected by the radio signal 302
to the transmission determining unit 14 and the reception determining
unit 22.

[0071] The analyzing unit 20 receives the reception signal 172 outputted
by the radio reception unit 17. The analyzing unit 20 separates the
reception signal 172 into the LAN signal and the alarm signal. The LAN
signal is data to be transmitted to the user network 40. The analyzing
unit 20 outputs the separated LAN signal to the frame integrating unit 23
as the integration LAN signal 201.

[0072] The analyzing unit 20 detects an error of the reception signal 172
using the alarm signal separated from the reception signal 172 and the
error detection code which is inserted at the generating unit of the
radio-opposed station, and outputs it as the reception alarm signal 202.
If the error occurs and exceeds a predetermined reference value, the
analyzing unit 20 generates the alarm information, adds the alarm
information to the reception alarm signal 202, and outputs the signal 202
with the information to the transmission determining 14.

[0073] The analyzing unit 21 outputs the LAN signal separated from the
reception signal 193 to the frame integrating unit 23 as the integration
LAN signal 211, like the analyzing unit 20. The analyzing unit 21 outputs
the alarm signal separated from the reception signal 193 as the reception
alarm signal 212. The analyzing unit 21 adds the alarm information
detected in the reception signal 193 to the reception alarm signal 212,
and outputs it to the transmission determining 14.

[0074] The frame integrating unit 23 receives the integration LAN signal
201 and the integration LAN signal 211. If both the integration LAN
signal 201 and the integration LAN signal 211 are not invalid, the frame
integrating unit 23 integrates the two signals to generate the MAC frame.
If one of the integration LAN signal 201 and the integration LAN signal
211 is invalid data, the frame integrating unit 23 generates the MAC
frame using the other integration LAN signal. As a result, the frame
integrating unit 23 restores the MAC frame before division at the time of
transmission. The frame integrating unit 23 outputs the integrated MAC
frame to the user network 40 as the external output LAN signal 231.

[0075] A frame integration procedure in the frame integrating unit 23 is
described with reference to FIG. 4.

[0076]FIG. 4 illustrates a configuration of the frame integrating unit
23. In the frame integrating unit 23 shown in FIG. 4, the integration LAN
signal 201 and the integration LAN signal 211 which are transmitted from
the analyzing unit 20 and the analyzing unit 21 enter a delay correcting
unit 23_1 and a delay correcting unit 23_3, respectively.

[0077] The delay correcting unit 23_1 and the delay correcting unit 23_3
detect a difference of propagation delay which occurs due to a difference
of electrical length of the radio transmitting/receiving units 15 and 19,
wiring in and/or between devices, or the radio transmission path. The
delay correcting unit 23_1 and the delay correcting unit 23_3,
specifically, detect the synchronization patterns which are inserted in
the generating unit 12 and the generating unit 13, and compare the
detection timing with each other, respectively. As a result, the delay
correcting unit 23_1 and the delay correcting unit 23_3 can detect the
difference of the propagation delay between the integration LAN signal
201 and the integration LAN signal 211.

[0078] The delay correcting unit 23_1 and the delay correcting unit 23_3
shift the integration LAN signal 201 and the integration LAN signal 211
each other, respectively, and minimize the difference of the propagation
delay between the integration LAN signal 201 and the integration LAN
signal 211. The minimum unit by which the integration LAN signal 201 or
the integration LAN signal 211 is shifted is a unit of the clock
generated from the signals.

[0079] In the present exemplary embodiment, after the MAC frame is divided
by the frame dividing unit, the divided MAC frames are transmitted on the
radio transmission paths and demodulated by the different radio receiving
units. Therefore, it is highly likely that when the transmission speed of
an extension signal 23_21 is equal to that of an extension signal 23_41,
phases of the signals do not accord with each other even if the delay
correction of the clock unit is performed in the delay correcting unit
23_1 and the delay correcting unit 23_3. Dynamic phase fluctuation may
occur in transmission data because of fading due to change of the
propagation condition of a radio wave. For the reason described above, a
phase difference between the pieces of data of the two systems may
temporally fluctuate. If the data of the two systems are processed by the
clock which is synchronized with one of the data thereof, the other data
may not be read out accurately since the phase of the other data deviates
from the clock.

[0080] In the first exemplary embodiment, the frame integrating unit 23
performs processing, i.e. bit width extension, with respect to the data
in an extending unit 23_2 and an extending unit 23_4. Procedures on the
bit width extension are described below.

[0081] The bit width extension means processing in which width of one bit
of the data is extended without changing the data transmission speed by
processing data to be processed in parallel.

[0083] Suppose that two data lines (hereinafter referred to as "system 1
data", "system 2 data") which are synchronized with different clocks are
read out at a falling edge of the clock generated from one data line
thereof. When the phase difference between the system 1 data and the
system 2 data exists, if timing when a clock which is synchronized with
the system 1 data reads out the system 2 data accords with a changing
point of the system, the data of the system which is not synchronized
with the clock may not be correctly read out.

[0084] In FIG. 5, (a) is a system 1 clock, (b) is the system 1 data, (c)
is a system 2 clock, and (d) is the system 2 data. Since phase adjustment
of the data is performed per a clock unit, if the phase difference
between the system 1 data (b) and the system 2 data (d) is around half of
a cycle of the clock as shown in FIG. 5, it is not possible to perform
adjustment so that the phase difference between the system 1 data and the
system 2 data becomes further small.

[0085] FIGS. 5 (a) to (d) illustrate falling timing of the system 1
division clock (a) (K) and falling timing of the system 2 division clock
(c) (L). If the system 1 data (b) and the system 2 data (d) are read out
at the falling timing of the system 1 clock (a) which is synchronized
with the system 1 data ((K) in FIG. 5), the falling timing accords with
the changing point of the system 2 data (d). In this case, the system 2
data (d) may not be read out correctly.

[0086] If the system 1 data (b) and the system 2 data (d) are read out at
the falling timing of the system 2 clock (c) ((L) in FIG. 5), the falling
timing accords with the changing point of the system 1 data (b). In this
case, the system 1 data (b) may not be read out correctly.

[0087] That is, if the phase difference between the system 1 data (b) and
the system 2 data (d) is around half of a cycle of the clock, even though
the clock of the system 1 or the system 2 is used, both the system 1 data
(b) and the system 2 data (d) may not be read out correctly.

[0088] In the bit width extension, n pieces of data (n is a integer equal
to or greater than 2) are processed in parallel to increase a data width
by n times. By performing the bit width extension processing, even if the
phase relationship of the data is as shown by FIG. 5 (a) to (d), the
system 1 data and the system 2 data can be read out by using a clock
which is generated from any one of the system 1 data and the system 2
data.

[0089] FIGS. 5 (e) to (h) illustrate a clock and data which are shown when
the bit width of the data is extended to be doubled through the bit width
extension.

[0090] In FIG. 5, a system 1 division clock (e) is a divide-by-2 clock of
the system 1 clock, (f) is the system 1 data which is processed in
parallel in two, (g) is a divide-by-2 clock of the system 2 clock, and
(h) is the system 2 data which is processed in parallel in two. FIGS. 5
(e) to (h) illustrate falling timing of the system 1 division clock (e)
(M) and falling timing of the system 2 divide-by-2 clock (g) (N).

[0091] As shown in FIG. 5, the system 1 data (f) and the system 2 data (h)
are the data, a bit width of which is extended. In the system 1 data (f)
and the system 2 data (h), parallelized data is read out and processed at
the same time by a clock. A clock speed in each processing may be a half
of the clock without bit width extension processing. The bit width
extension operation corresponds to the transition from S2 to S4, and the
transition from S3 to S5.

[0092] The system 1 data (f) with the extended bit width and the system 2
data (h) with the extended bit width are parallelized in two, while
synchronizing the system 1 data (b) and the system 2 data (d) with the
clock (a) and the clock (c), respectively. The phase difference between
the system 1 data (f) with the extended bit width and the system 2 data
(h) with the extended bit width is equal to the phase difference between
the system 1 data (b) and the system 2 data (d) (i.e. a half cycle of the
clock (a) or the clock (c)).

[0093] The phase difference between the system 1 data (f) with the
extended bit width and the system 2 data (h) with the extended bit width
is a half cycle of the clock (a) or the clock (c), and the length of the
system 1 data (f) and the system 2 data (h) is doubled by
parallelization.

[0094] Here, falling of the system 1 division clock (e) and the system 2
division clock (g), and the data changing points of the system 1 data (f)
and the system 2 data (h) are focused. The falling timing of the system 1
clock (e) and the system 2 clock (g) ((M), (N) in FIG. 5) are located at
positions which are different from the changing points of the data (f)
and the data (h). Consequently, the data (f) and the data (h) can be read
out correctly using any one of the system 1 clock (e) and the clock (g).

[0095] In the bit width extension operation, the data is parallelized to
extend the data width. By extending the data width, the timing of reading
out the clocks of systems 1 and 2 ((M), (N) in FIG. 5) can be located at
the positions other than the changing points of the data. The signals
with different phases can be read out using any clock of the systems 1
and 2. In the first exemplary embodiment, the integration LAN signal 201
and the integration LAN signal 211 correspond to the system 1 data (or
the system 2 data) and the system 2 data (or the system 1 data),
respectively.

[0096] In descriptions above, the parallel number of the data is two, and
the clock is divided by two. If the parallel number of the data (i.e.
division number of the clock) is equal to or greater than two, the
similar effect is possible.

[0097] In FIG. 4, the extending unit 23_2 and the extending unit 23_4
output the integration LAN signal 201 and the integration LAN signal 211,
bit width extension of which is performed, to a retiming unit 23_5 as the
extension signal 23_21 and the extension signal 23_41, respectively.

[0098] The retiming unit 23_5 chooses a system which is not invalid data
from one of the extension signal 23_21 and the extension signal 23_41.
The retiming unit 23_5 compares a phase of a clock of the chosen signal
with a phase of a retiming clock 23_61 outputted by a PLL unit 23_6, and
outputs a frequency controlling signal 23_51 generated based on the
comparison result to the PLL unit to control the PLL. As a result, the
retiming unit 23_5 can synchronize the retiming clock 23_61 with the
chosen clock.

[0099] The extension signal 23_21 and the extension signal 23_41 have the
bit width extension processing in the extending unit 23_2 and the
extending unit 23_4, respectively. Based on the operation described using
FIG. 5, the retiming unit 23_5 performs retiming of the data of both the
extension signal 23_21 and the extension signal 23_41 using the retiming
clock 23_61 regenerated from one of the data.

[0100] The retiming unit 23_5 combines the extension signal 23_21 and the
extension signal 23_41 on which retiming is performed so that BYTE data,
in which the extension signal 23_21 is arranged in an upper bit string
and the extension signal 23_41 is arranged in a lower bit string, is
configured. This corresponds to the transition from S4 to S6 and the
transition from S5 to S6, in FIG. 2.

[0101] The configured BYTE data is outputted to a shortening unit 23_7 as
a retiming signal 23_52 (S6 in FIG. 2).

[0102] In descriptions above, the BYTE data is configured using the
extension signal 23_21 and the extension signal 23_41 if the both signals
are normal data. If one of the extension signals is invalid data, the
retiming unit 23_5 configures the BYTE data only using the normal
extension signal. This corresponds to the transition from S14 to S16.

[0103] The shortening unit 23_7 receives the retiming signal 23_52
outputted by the retiming unit 23_5. The shortening unit 23_7 performs
operations opposite to the bit width extension which is performed by the
extending unit 23_2 and the extending unit 23_4 (transition from S6 to S7
in FIG. 3) and changes the data width into the original width. The
shortening unit 23_7 outputs the data with the original bit width to the
user network 40 in FIG. 1 as the external output LAN signal 231.

[0104] The retiming unit 23_5 chooses one of the extension signal 23_21
and the extension signal 23_41 as a clock source, and outputs it to the
PLL unit 23_6. When the retiming unit 23_5 uses by changing the clock
source with a selector by itself without using a PLL circuit,
instantaneous interruption of the clock or jump of a clock phase may
occur. The instantaneous interruption of the clock or the jump of a clock
phase causes occurrence of a signal error. In the first exemplary
embodiment, therefore, the retiming unit 23_5 works according to the
clock outputted by the PLL unit 23_6. Thereby, probability, that the
signal error occurs, in the retiming unit 23_5, due to the instantaneous
interruption of the clock or the jump of a clock phase at the time of
changing the clock source, may be reduced.

[0105] The delay correction method and the retiming method in the frame
integrating unit 23 which are described above are known as an
uninterrupted switching method in a digital radio transmission field.
Therefore, detailed descriptions are omitted.

[0106] In the first exemplary embodiment, the transmission determining
unit 14 in FIG. 1 outputs an alarm state which the radio transmitter
apparatus 10 holds to the generating unit 12 and the generating unit 13
as the multiple alarm signals 142 and 143, respectively. An alarm
included in the alarm state which is outputted from the transmission
determining unit 14 includes a reception alarm due to a device failure of
the radio transmitting/receiving units 15 and 19 and/or environment
change in the radio transmission path, a signal error alarm on the
reception signal, and a detection alarm on the invalid data.

[0107] The reception alarm due to a device failure of the radio
transmitting/receiving units and/or environment change in the radio
transmission path is detected in the radio alarm signal 171 and the radio
alarm signal 192. The signal error alarm on the reception signal and the
detection alarm on the invalid data are detected in the reception alarm
signal 202 and the reception alarm signal 212.

[0108] When detecting the reception alarm detected by the radio
transmitter apparatus 30 or the signal error alarm of the reception
signal in the reception alarm signal 202 or the reception alarm signal
212, the transmission determining unit 14 determines that a signal of the
system in which these alarms are detected is invalid data. Determining
that a signal of the system in which these alarms are detected is invalid
data, the transmission determining unit 14 outputs the division control
signal 141 instructing to determine that the signal of the system is the
invalid data to the frame dividing unit 11.

[0109] The reception determining unit 22 receives the radio alarm signal
171 and the radio alarm signal 192. The reception determining unit 22
detects a device failure alarm of the radio transmitting/receiving unit
and/or a reception power reduction alarm due to the environment change on
the radio transmission path in these radio alarm signals. Detecting the
device failure alarm or the reception power reduction alarm, the
reception determining unit 22 outputs a control signal determining the
data of the system in which the alarm occurs is the invalid data as the
integration control signals 221 and 222.

[0110] A first effect of the radio transmission system of the first
exemplary embodiment described above is that it is possible to suppress
complexity of configuration and price increase in the transmitter
apparatus with the adaptive modulation function. In the radio
transmission system of the first exemplary embodiment, the radio
transmitter apparatus includes the adaptive modulation function. In the
radio transmitter apparatus, the radio transmitting units of the two
systems modulate data using the same modulation scheme. That is, in the
radio transmission system of the first exemplary embodiment, the
transmitting apparatus on the transmission side can choose a suitable
modulation scheme depending on conditions of a plurality of the
transmission paths and the transmitting apparatus on the reception side
can receive divided data at the same modulation speed. Accordingly the
transmitting apparatus on the reception side does not require memory for
absorbing a difference of transmission speeds between the respective
reception data and can suppress complexity of the configuration and price
increase in the transmitter apparatus with the adaptive modulation
function.

[0111] A second effect of the radio transmission system of the first
exemplary embodiment is that it is possible to easily increase a radio
transmission capacity in the radio transmitting apparatus for
transmitting the MAC frame of the LAN signal from the user network to a
single opposed station wirelessly.

[0112] Procedures obtaining the effects are as follows. The radio
transmitter apparatus of the first exemplary embodiment divides the MAC
frame into two parts in its own apparatus and inserts the synchronization
pattern at a constant period. The radio transmitter apparatus of the
first exemplary embodiment transmits the divided data from the radio
transmitting/receiving units of the two systems arranged in its own
apparatus to the radio-opposed stations. The opposed radio transmitter
apparatus detects the propagation delay difference which occurs due to
the electric length difference in the radio transmitting/receiving unit,
the cable, the radio transmission path, and the like, by using the
synchronization pattern in the reception signal. The opposed radio
transmitter apparatus adjusts the phases of both of the MAC frames to
absorb the propagation delay difference. After absorbing the propagation
delay difference, the radio transmitter apparatus integrates the MAC
frames which are divided in two parts into a single MAC frame. As a
result, the radio transmission system of the first exemplary embodiment
may include the transmission capacity which is twice as much as that of
MAC frame transmission on the single radio transmission path.

[0113] A third effect of the first exemplary embodiment is that even
though it is impossible to transmit data because of a device failure of
one of the radio transmitting/receiving units and/or degradation of a
propagation condition of the radio transmission path, signal transmission
may be performed using the other normal system.

[0114] That is because the generating unit of the radio transmitter
apparatus inserts the signal error detecting code to perform the radio
transmission. The radio transmitter apparatus detects abnormality on the
radio transmission path based on the detection result of the reception
power reduction alarm in the radio transmitting/receiving unit and the
result of signal error detection in the analyzing unit. When detecting
abnormality on the radio transmission path, the radio transmitter
apparatus informs the radio-opposed station of the abnormal condition of
the system on which abnormality is detected. In the radio transmitter
apparatus, if the analyzing unit detects the information on the abnormal
condition from the radio-opposed station, the frame dividing unit stops
dividing the MAC frame. The radio transmitter apparatus transmits the
invalid data to the system in which the abnormal condition occurs, and
the MAC frame data only to the system which normally works. In the radio
transmitter apparatus opposed thereto, the frame integrating unit
integrates two divided signals to form the MAC frame if the integration
LAN signal outputted by the analyzing unit is normal. If one of received
divided data is the invalid data, the radio transmitter apparatus
restores the MAC frame using only the data which is received from the
normal system. As a result, in the radio transmission system of the first
exemplary embodiment, even if abnormality occurs in one system, signal
transmission may continue in the other normal system.

[0115] A fourth effect of the first exemplary embodiment is that it is
possible to avoid occurrence of order replacement of the MAC frame which
occurs when the MAC frames having random length are delivered and
transmitted to a plurality of the transmission paths.

[0116] That is because in the first exemplary embodiment, the radio
transmitter apparatus does not allocate the MAC frames to respective
transmission path in a unit of the MAC frame, but divide inputted MAC
frame into two parts and transmits them without replacing the order of
the MAC frames. As a result, the radio transmitter apparatus opposed
thereto integrates the data received from the radio transmission path in
order of reception to restore the MAC frame of the LAN signal. The radio
transmission system of the first exemplary embodiment can avoid
occurrence of order replacement of the MAC frame.

[0117] In the first exemplary embodiment, the adaptive modulation
determining unit 18 chooses the modulation scheme on the basis of the
magnitude relationship between the radio reception power in the opposed
radio transmitter apparatus 30 and a predetermined threshold value.
However, the adaptive modulation determining unit 18 may choose the
modulation scheme based on other information. The opposed radio
transmitter apparatus 30 may transmit, for example, CNR (Carrier to Noise
Ratio, i.e. Carrier wave power to Noise power Ratio) of the signal
received from the radio transmitter apparatus 10, and/or an error rate of
the reception signal to the radio transmitter apparatus 10. The adaptive
modulation determining unit 18 of the radio transmitter apparatus 10 may
choose the modulation scheme of the radio transmitting unit 16 or the
radio transmitting unit 16A based on the CNR or the error rate received
from the radio transmitter apparatus 30.

[0118] In the first exemplary embodiment, the adaptive modulation
determining units 18 and 18A of the radio transmitter apparatus 10 choose
the modulation scheme so that the transmission speeds of the transmission
signals 121 and 131 accord with each other. However, if a difference in
the transmission speeds between the transmission signals 121 and 131 is
small, the problem of complexity of the configuration of the radio
transmitter apparatus 30 for receiving the transmission signals 121 and
131 and price increase thereof may not occur. For example, if the radio
transmitter apparatus on the reception side does not require memory with
a large amount of capacity even though the transmission signals 121 and
131 differ in the transmission speed from each other, the effect of the
invention, in which it is possible to suppress complexity of the
configuration of the radio transmitter apparatus and price increase
thereof, is not lost,

[0119] When the radio transmitter apparatus on the reception side allows
some degree of difference of the transmission speeds, the adaptive
modulation determining units 18 and 18A may not necessarily decide the
modulation scheme having the same transmission speed.

[0120] For example, the adaptive modulation determining units 18 and 18A
may decide the modulation scheme so that the difference in the
transmission speeds between the modulation schemes decided in the unit 18
and 18A falls within a predetermined range.

[0121] The adaptive modulation determining units 18 and 18A may decide the
range of the difference in the transmission speeds between the modulation
schemes to be decided based on the allowable range of the transmission
speed for the receiver apparatus.

Second Exemplary Embodiment

[0122] In the first exemplary embodiment, the radio transmitter apparatus
include the configuration in which the inputted MAC frame is divided into
two parts and transmitted. The MAC frame is not necessarily divided into
two parts.

[0123]FIG. 6 is a diagram illustrating a radio transmitter apparatus of a
second exemplary embodiment of the invention. A radio transmitter
apparatus 10_1 shown in FIG. 6 includes a function for dividing the MAC
frame into four parts and transmitting them to an opposed radio
transmitter apparatus 30_1. In FIG. 6, an operation of each part in the
radio transmitter apparatus 10_1 is the same as that of the part with the
same name in the radio transmitter apparatus 10. In FIG. 6, therefore,
description on detailed connection of respective parts and the inside of
the radio transmitter apparatus is omitted.

[0124] In FIG. 6, the radio transmitter apparatus 10_1 faces the radio
transmitter apparatus 30_1 and the apparatuses transmit the MAC frame to
each other. The radio transmitter apparatus 10_1 divides the external LAN
signal 100 which is inputted from the user network 40 and transmits them
to the radio transmitter apparatus 30_1 as a radio signal. The radio
transmitter apparatus 30_1 restores data from the radio signal received
from the radio transmitter apparatus 10_1 and outputs it to the user
network 50 as the external output LAN signal 501.

[0125] The radio transmitter apparatus 30_1 divides the external LAN
signal 502 which is inputted from the user network 50 and transmits them
to the radio transmitter apparatus 10_1 as a radio signal. The radio
transmitter apparatus 10_1 restores data from the radio signal received
from the radio transmitter apparatus 30_1 and outputs it to the user
network 40 as the external output LAN signal 231.

[0126] The radio transmission apparatus shown in FIG. 6 divides the MAC
frame into four parts in the frame dividing unit 11 and transmits them.
For this, the apparatus includes four generating units 12, 13, 12_1, and
13_1, four analyzing units 20, 21, 20_1, and 21_1, and four radio
transmitting/receiving units 15, 19, 15_1, and 19_1. Each radio
transmitting/receiving unit includes the adaptive modulation function.
The four radio transmitting/receiving units 15, 19, 15_1, and 19_1 inform
of information of the modulation scheme the radio transmitter apparatus
each other, and operate so that all of the radio transmitting/receiving
units use the modulation scheme with the same transmission speed.

[0127] A configuration and operations of each part of the radio
transmitter apparatus 10A are similar to those of the radio transmitter
apparatus 10 described in the first exemplary embodiment. Therefore,
detailed descriptions on the parts are omitted.

[0128] The radio transmitting/receiving unit 15 modulates the MAC frame
which is outputted from the generating unit 12 and divided, and outputs
them as the radio signal 161. The radio signal 161 is transmitted to the
radio transmitter apparatus 30_1 through the antennas 10A and 30A.

[0129] Similarly, the generating units 13, 12_1 and 13_1 output divided
frame to the radio transmitting/receiving units 19, 15_1 and 19_1,
respectively. The radio transmitting/receiving units 19, 15_1 and 19_1
modulate inputted signals and output the radio signals 191, 101 and 102,
respectively. The radio signals 191, 101 and 102 are transmitted to the
radio transmitter apparatus 30_1 through the antennas 10C, 10E and 10G,
and the antennas 30C, 30E and 30G, respectively.

[0130] The radio transmitting/receiving unit 15 receives the radio signal
301 which is transmitted by the radio transmitter apparatus 30_1 through
the antennas 30B and 10B. The radio transmitting/receiving unit 15
demodulates the radio signal 301 and outputs it to the analyzing unit 20.
The analyzing unit 20 separates the divided MAC frame 23 from the
demodulated signal, and outputs them to the frame integrating unit 23.
The frame integrating unit 23 integrates the divided frames which are
received from the analyzing units 20, 21, 20_1 and 21_1, and outputs it
to the user network 40 as the external output LAN signal 231.

[0131] Similarly, the radio transmitting/receiving units 19, 15_1 and 19_1
receive the radio signals 302, 303 and 304 which are transmitted by the
radio transmitter apparatus 30_1 through the antennas 30D, 30F and 30H,
and 10D, 10F and 10H, respectively. The radio transmitting/receiving
units 19, 15_1 and 19_1 demodulate these radio signals and output them to
the analyzing units 21, 20_1 and 21_1, respectively. Each analyzing unit
separates the MAC frame which is divided from the demodulated signal, and
outputs it to the frame integrating unit 23.

[0132] Transmitting the MAC frame after dividing it in four parts, the
radio transmission system of the second exemplary embodiment can transmit
the MAC frame at a high transmission speed, compared with the first
exemplary embodiment, in addition to the effect of the first exemplary
embodiment.

[0133] In the first and second exemplary embodiment, the invention is
explained with the case of its application to the radio transmission
system with the radio transmitter apparatus. However, the invention is
not limited to radio transmission. The invention is applicable to, for
example, a wired transmitter apparatus with a coaxial cable or an optical
fiber.

[0134] The scheme of the radio transmission targeted by the invention is
not limited a scheme using a radio wave. The invention is applicable to,
for example, a transmitter apparatus using an optical space transmission
scheme.

Third Exemplary Embodiment

[0135]FIG. 7 is a diagram illustrating a configuration of a transmitter
apparatus of a third exemplary embodiment of the invention. In FIG. 7, a
transmitter apparatus 700 includes a dividing unit 701, N pieces of
transmitting units 702_1 to 702_N,N pieces of transmitting units 702_1 to
702_N, and a modulation scheme deciding unit 703.

[0136] The dividing unit 701 divides inputted data into a plurality of
pierces. The transmitting units 702_1 to 702_N transmit divided data on
transmission paths. The modulation scheme deciding unit 703 decides the
modulation scheme, used by transmitting means, of schemes associated with
conditions of the transmission paths so that the difference in the
transmission speeds between a plurality of pieces of data transmitted by
the plurality of transmitting means falls within a predetermined range.

[0137] The transmitter apparatus of FIG. 7 transmits data divided by the
dividing unit 701 on the transmission paths using the plurality of
transmitting units 702_1 to 702_N. The modulation schemes used by the
transmitting units are associated with conditions of the transmission
paths where the data is transmitted. The modulation scheme deciding unit
703 decides the modulation schemes by which the transmitting unit 702_1
to 702_N modulate the data from among these modulation schemes so that
the difference in the transmission speeds between a plurality of pieces
of data transmitted by the plurality of transmitting means falls within a
predetermined range.

[0138] When the modulation scheme deciding unit 703 decides the modulation
schemes used by the transmitting units 702_1 to 702_N based on the
modulation schemes associated with the transmitting units 702_1 to 702_N,
complexity of a configuration of the transmitter apparatus on the
reception side which is not shown, and price increase thereof are
avoided.

[0139] If the modulation scheme deciding unit 703 restricts the difference
in the transmission speeds between the modulation schemes simultaneously
used by the transmitting units 702_1 to 702_N, the range of the speeds of
the modulation scheme to be processed at the same time and data are
limited in the transmitter apparatus on the reception side. When the
speeds of the modulation schemes falls within a predetermined range, the
transmitter apparatus does not require memory with a large capacity for
absorbing the difference in the transmission speeds between respective
pieces of reception data.

[0140] Consequently, the transmitter apparatus of the third exemplary
embodiment enable to suppress complexity of the transmitter apparatus and
price increase thereof, if the transmitter apparatus with the adaptive
modulation function divides data and transmits them.

[0141] While having described an invention of the present application
referring to the embodiments 1 to 3, the invention of the present
application is not limited to the above mentioned embodiments 1 to 3. It
is to be understood that to the configurations and details of the
invention of the present application, various changes can be made within
the scope of the invention of the present application by those skilled in
the art.

[0142] This application is based upon and claims the benefit of priority
from Japanese patent application No. 2010-058982 filed on Mar. 16, 2010,
the disclosure of which is incorporated herein in its entirety by
reference.